As a battery pack including plural battery modules assembled, each battery module including a battery accommodated in a case, Japanese Patent Application Publication No. 2013-12458 below discloses a battery pack in which plural battery modules are stacked on top of each other in the up and down direction.
When gas is emitted from a battery which is accommodated in a case of a battery module situated in lower part because of battery abnormalities, heat of the gas emitted from the battery situated in the lower part influences batteries of the other battery modules located in upper part and could shorten the lives of the batteries.
If gas is emitted from one of the batteries because of battery abnormalities, the emitted gas needs to be properly exhausted to the outside of the case.